[Haskell-beginners] netwire and "dynamic" list of objects
nathan.huesken at posteo.de
Tue Apr 10 17:07:47 CEST 2012
Firstly, thanks for the answer.
Ok, I made another attempt. I have a function, to output the state of
objectWire :: StdGen -> MyWire () ObjectState
The random generator is used to create the initial state. Now I want to
handle a dynamic set of objects. This is my attempt:
wire :: MyWire () State
wire = proc _ -> do
rnds <- Wire.delay initRnds -< (tail rnds)
let rnd = head rnds --Get a fresh random generator everytime
--For now, only one new object every call
let newObjWires = [objectWire rnd]
--Start with newObjWires and add newObjWires everytime (1. Error)
objWires <- Wire.delay newObjWires -< newObjWires ++ objWires
oss <- distribute objWires -< () -- 2. Error
Wire.identity -< GameState rnds ss
initRnds = stdgens $ mkStdGen 0
Now I get
Not in scope: `newObjWires'
at the 1. Error and
Not in scope: `objWires'
at the 2. Error.
OK, I am guessing that I may not use newObjWires/objWires as parameters
to the functions creating the wires.
But I do not understand how to use any of Control.Wire.Trans.Combine to
handle my dynamic set of wires.
On 04/10/2012 01:57 PM, Ertugrul Söylemez wrote:
> Nathan Hüsken <nathan.huesken at posteo.de> wrote:
>> I have a simple SDL based graphic demo, which I am trying (for
>> educational purposes) to rewrite utilizing netwire.
>> The demo basically consists of a State which contains a list of object
>> But I avoided rewriting "updateState" in wire format. But I have no
>> Idea how to do that.
>> How do I handle a dynamic list of objects in a wire?
> Well, you are not really using FRP here. You are just forcing this
> application into the FRP model. Your only behavior is the application
> itself. This works, but buys you nothing.
> The first step to actually making use of FRP here is to get rid of the
> concept of "updating" something. Express your game objects themselves
> as wires:
> player :: GameWire (Input, [Wall]) Player
> wall :: GameWire a Wall
> enemy :: GameWire (Player, [Wall]) Enemy
> This allows you to write static game worlds. After that you can move to
> dynamic game worlds using wire transformers from
> Control.Wire.Trans.Combine. It is also pretty straightforward to write
> your own wire transformers for this purpose. You probably want to do
> that later -- just look at the source code.
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